1. Field of Invention
This invention relates in general to oil and gas production, and in particular to a pressure equalization system for an electrical submersible pumping (ESP) system.
2. Description of Prior Art
Submersible pumping systems are often used in hydrocarbon producing wells for pumping fluids from within the wellbore to the surface. These fluids are generally liquids and include produced liquid hydrocarbon as well as water. One type of system used employs an electrical submersible pump (ESP). ESPs are typically disposed at the end of a length of production tubing and have an electrically powered motor. Often, electrical power may be supplied to the pump motor via a cable. The pumping unit is usually disposed within the well bore just above where perforations are made into a hydrocarbon producing zone. This placement thereby allows the produced fluids to flow past the outer surface of the pumping motor and provide a cooling effect.
ESPs are generally elongate so they can be inserted within a producing wellbore where the motor usually is on the lowermost end of the ESP assembly. The motor is typically protected by dielectric fluid housed in the ESP motor. A seal section, which also contains dielectric fluid, usually provides pressure equalization between the dielectric fluid and conditions ambient to the ESP. As the ESP is lowered within a wellbore, fluid static head increases well above atmospheric pressure. Without equalizing pressure between the dielectric fluid and ambient, a pressure gradient could be generated sufficient to breach pressure seals in the ESP assembly.